Electric-call system.



(No Mqdal.)

H. IL DUMAS. ELECTRIC CALL SYSTEM.

(Application filed Apr. 29, 1898.)

Patented Sept. 12, I899.

NrTnn STATES PATENT Prion.

HARRY M. DUMAS, OF DETROIT, MICHIGAN.

ELECTRIC-CALL SYSTEM.

SPEGIFICATION forming part of Letters Patent No. 632,964, dated September 12, 1899.

Application filed April 29,1898. Serial No. 679,250. (No model.)

To coZZ whom it may concern.-

Be it known that I, HARRY M. DUMAS, a citizen of the United States, residing at Detroit, in the .county of IVayne and State of Michigan, have invented certain new and useful Improvements in Electric Call Systoms, of which the following is a specification, reference being had therein to the accompanying drawings.

My invention relates to electric-call systems in which a plurality of call instruments are arranged at different points of a common normally-closed electric circuit including the receiving instrument at the central station, each call instrument comprising circuit-interrupting mechanism adapted to produce its individual call. Call systems of this character are in common use, but as generally constructed are unreliable, so that the person operating the call mechanism cannot be certain that the signal has been transmitted to the central station. This is for the reason that if the main circuit becomes inoperative either through a break or a short circuit the call mechanism may still be operated and will give no indication to the operator of the inoperative condition of the circuit.

It isthe object of my invention to eliminate this element of uncertainty; and to this end my invention consists in the means employed forlocking the call mechanism against operation excepting when the circuit is in operative condition; further, in the means for still operating the calls when the circuit is in an abnormal condition by reason of a break, and, further, in the peculiar construction, arrangement, and combination of parts.

In the drawings, Figure 1 is a diagram of my call system. Fig. 2 is an elevation of one of the call instruments with the casing removed and the electric connections shown in diagrams. Fig. 3 is a perspective view showing the lock and electromagnetic releasing device for said call mechanism. Fig. 4 is an elevation thereof with the parts in a difiierent cuit-interrupting mechanism E, for which I preferably employ the usual form of device. This comprises the contact arm a, bearing against the notched contact-wheel Z), which is connected with a gear-train having the winding-shaft c, a spring d, and an escapement e, the whole being so arranged that by turning the actuating crank-handle f the spring may be wound and in unwinding will actuate the gear-train and rotate the contact-wheel, causing it to break and make contact with the arm a and send the particular signal indicating the box. To this interrupting mechanism I apply myautomatic locking and releasing device, which, as shown in the drawings, is constructed as follows:

F is acontact-arm secured to the windingshaft 0 and normally bearing upon the contact G, which is electrically connected to the binding-post H.

I is a segmental contact arranged concentrically with the shaft 0, one end of which extends in proximity to the contact G.

J is 'an electromagnet, the terminals of which are connected, respectively, with the segmental contact I and the binding-post H. K is the armature therefor, and L is a hooked arm connected to said armature, extending into the path of the arm F and adapted when the magnet is not energized to engage with said arm and prevent the turning of the crank-handle f.

M is a binding-post connected to the con tact-arm a, to which post one of the wires of the main circuit A is connected, the other wire being connected to the binding-post H.

The parts being thus constructed and arranged, when the electric circuit is in its normal closed condition the current passes through the binding-post M to the contactarm a, thence through the contact-wheel l) and connecting mechanism to the movable contact-arm F, and through the contact G to the binding-post H.

In the operation of the call the turning of the crank-handle f will cause the movable thereby permitting of the further movement of said arm and the turning of the crankhandle fto wind the spring, which in unwinding will cause the movement of the mechanism and the sending of the call. If, however, there is a failure of current in the main circuit, owing to a break therein or from any other cause, the handlef can only be turned sufficiently to move the contact-arm F from the contact 0 to the contact I,when the hooked arm L will engage with the arm F and hold it and the crank from further movement. Thus the operator will be apprised of the fact that the system is disarranged. To prevent the interference of one call with another, the resistance of the magnets J is so proportioned to the strength of the current in the circuit that if a second magnet is cut in after one is already included in the circuit the resistance will be so great that said second magnet cannot be energized, and its mechanism will therefore remain locked. In order to make the system still operative when a break occurs at some one point therein, I preferably provide each of the call-boxes with a ground connection and a normally open switch, which is adapted to close connect-ion between said ground connection and either one of the hinding-posts 1-1 and H.

In the drawingsl have shown two push-but tons N and 0, arranged in connection between a binding-post P and the posts H and M, respectively, the post P having the ground conncction Q connected therewith. At the central station, on one side of the battery, is arranged a switch R foropening the main circuit and connecting the battery with a ground S, and beyond this switch is a spring-jack T for connecting in a second receiving instrument U and a battery V, one pole of which is grounded. WVith this arrangement as soon as a break or ground occurs in the main circuit the switch R is shifted at the central station and the auxiliary receiving instrument U and battery V connected in, as above described. If, now, an attemptis made to operate any one of the call-boxes in the ordinary way, the mechanism will remain locked; but the operator may then push one of the buttonsas, for example, the button Nand make another attempt to turn the crankf. If the break is not in that part of the main circuit between the ground S and the call-box which includes the battery O and the receiver B, a complete circuit will be established which will energize the magnet J and permitthe mechanism to be operated, sending the call which is received on the instrument '8 at the central station. Should, however, the break be in that part of the main circuit, (as at X,) the circuit will not be completed by operating the push-button N, and the mechanism will remain locked. The operator then releases the push-button N and presses the button 0, which will complete a circuit through the other portion of the main circuit, including the auxiliary receiver U and battery V, permitting of the operation of the boX, which will operate the auxiliary receiver U. Thus it will be seen that the element of uncertainty is entirely eliminated from this call system, the operator being always informed as to whether or not the call has been sent, and, furthermore, when the system is in an abnormal condition he is still able to send in the call in the manner above described.

lVhat I claim as my invention is- 1. The combination with an electric-call circuit and call mechanism therefor, of an arm or handle for manually operating said mechanism, a lock for arresting the movement of said arm or handle before it can operate the said mechanism, an electromagnet for releasingsaid lock anda switch for cutting said magnet into said circuit adapted to be operated by said arm or handle in the initial movement thereof.

2. The combination with an electric-call circuit and call mechanism therefor, comprising a signal-wheel a spring-actuated train for rotating said wheel, and a manually-operable crank-handle for winding said spring; of a contact-arm secured in the shaft of said crank, a segmental plate with which said arm is adapted to contact after a limited movement, a locking-latch for arresting the movement of said arm and crank after the former has contacted with said segmental plate and an electromagnet for releasing said latch adapted to be cut into said circuit by the contacting of said arm with said segmental plate.

3. An electric-call system comprising a normally closed electric circuit, a plurality of manually-operable call mechanisms arranged at different points thereof, an automatic lock for each call mechanism, and a releasing electromagnet for each lock adapted to be cut into said circuit by the initial manual operation, said magnets being of such resistance that a second magnet cannot be energized by the current of the circuitif cut in, in series with a magnet previously cut in.

at. An electric-call system comprising a normally closed metallic circuit, call mechanism at the calling-point having an arm or handle for manually operating the same, a lock for arresting said arm, an electromagnet for releasing said lock adapted to be cut in said circuit upon the initial movement of said handle a normally open ground connection and means for connecting said ground to said circuit upon either side of said call mechanism and releasing the magnet for the purpose described.

In testimony whereof I affix my signature in presence of two witnesses.

HARRY M. DUMAS. lVitnesses:

M. B. ODoeHERTY, Or'ro F. BARTHEL. 

